From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1082C35646 for ; Fri, 21 Feb 2020 19:44:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9835E24650 for ; Fri, 21 Feb 2020 19:44:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="lYdo4NH8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726160AbgBUTod (ORCPT ); Fri, 21 Feb 2020 14:44:33 -0500 Received: from hqnvemgate26.nvidia.com ([216.228.121.65]:15668 "EHLO hqnvemgate26.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726443AbgBUTod (ORCPT ); Fri, 21 Feb 2020 14:44:33 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 21 Feb 2020 11:44:18 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 21 Feb 2020 11:44:32 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 21 Feb 2020 11:44:32 -0800 Received: from [10.2.166.200] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 21 Feb 2020 19:44:32 +0000 Subject: Re: [PATCH v7 11/24] mm: Move end_index check out of readahead loop To: Matthew Wilcox CC: , , , , , , , , , References: <20200219210103.32400-1-willy@infradead.org> <20200219210103.32400-12-willy@infradead.org> <20200221153537.GE24185@bombadil.infradead.org> From: John Hubbard X-Nvconfidentiality: public Message-ID: <1fd052ce-cd5e-60ce-e494-cbf6427d3ed3@nvidia.com> Date: Fri, 21 Feb 2020 11:41:28 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200221153537.GE24185@bombadil.infradead.org> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582314258; bh=pQKOwwEmNmp5lZ+eX1Ols5QNnW+OORTLQJDMCsPxtEc=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=lYdo4NH8M7SXphPat6doJg0oOA1V6kLXukQ7JIEh5FVkfFb0/CxKOhHQdMiRNYy87 Q6EhPR2Fph1xqpiZaGm+fIV8Ra4pJE8E5H2Ofj6LlTy0+Qb+/+y64EhZcbjIYXrOqI IXR7s2kX4Yi3hnWXNuj2sU2+Joh83jXJxvw8pHXSeKQS/7ccswnLmpLkros2lxWTg/ 2U8B/Ar6NYNMOQFqfCj3j5XpjUwSHVdi0BMHCh2YVMnazsUm42RddLEt+ZRAKHCaXa IlYO+1WyQ2QxlFvwnZy2R5xtgMwusy7sT9ZlwHQi2bqndUATGT9KLiH14aMZETjP0i ow4Jt857PEIiA== Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 2/21/20 7:35 AM, Matthew Wilcox wrote: > On Thu, Feb 20, 2020 at 07:50:39PM -0800, John Hubbard wrote: >> This tiny patch made me pause, because I wasn't sure at first of the exact >> intent of the lines above. Once I worked it out, it seemed like it might >> be helpful (or overkill??) to add a few hints for the reader, especially since >> there are no hints in the function's (minimal) documentation header. What >> do you think of this? >> >> /* >> * If we can't read *any* pages without going past the inodes's isize >> * limit, give up entirely: >> */ >> if (index > end_index) >> return; >> >> /* Cap nr_to_read, in order to avoid overflowing the ULONG type: */ >> if (index + nr_to_read < index) >> nr_to_read = ULONG_MAX - index + 1; >> >> /* Cap nr_to_read, to avoid reading past the inode's isize limit: */ >> if (index + nr_to_read >= end_index) >> nr_to_read = end_index - index + 1; > > A little verbose for my taste ... How about this? Mine too, actually. :) I think your version below looks good. thanks, -- John Hubbard NVIDIA > > end_index = (isize - 1) >> PAGE_SHIFT; > if (index > end_index) > return; > /* Avoid wrapping to the beginning of the file */ > if (index + nr_to_read < index) > nr_to_read = ULONG_MAX - index + 1; > /* Don't read past the page containing the last byte of the file */ > if (index + nr_to_read >= end_index) > nr_to_read = end_index - index + 1; >